Factbox - Syria's rebel groups

BEIRUT (Reuters) - Syria's rebel movement has been a constantly shifting array of groups and alliances since the uprising against President Bashar al-Assad began nearly three years ago, with opposition formations increasingly overtaken by Islamist groups.

As new leaders have emerged within the opposition, infighting reached a new level this month, with several rebel factions declaring war against the radical Islamic State of Iraq and the Levant (ISIL). Some 2,300 rebel fighters have died fighting each other this year alone.